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Of the major elements analyzed, Si showed negative correlations to Fe, Ti, Cr, Zn and P,
and positive correlations to Na, K and Rb. Aluminium showed large positive correlations to
Fe, Ti, Mn, Ni, Ga, Sr (N1 to N4), Zr, Th, and U.
A combination of PCA and cluster analysis also revealed geochemical discontinuities in
most of the soil profiles, in agreement with their complex stratigraphy. Some soils show
major geochemical discontinuities, as for example Nl, N5, N7, N8, N9, NIO and Nll; while
a few of them showed a more homogeneous elemental composition throughout the soil
profiles (N12, N13, N16, N17, N18, N19)
Table 2 Geochemical discontinuities (vertical bars between horizons) in the soil profiles
Volcanic area Soils
ITALY IT-Nl Ap-Bwl-Bw2 1 BC-C IT-N2 O-Al II BC1-BC2-C1 IT-N3 O 1 A1 -A2-AB-Bw 1 -Bw2 IT-N4 O 1A1-A2-A3 1 Bwl-Bw2
AZORES Is. AQ-N5 A1 II 2A-2B2-Bw/C II 2C1 AC-N6 A-ABw-2AB 1 2Bwl-2Bw2-2Bw3
ICELAND IC-N7 O-Alll A2 II A3-Bwl-Bw2-Bw3 II 2BCg IC-N8 Al-A2-Bwlll 2Bw II 3Bw-4C IC-N9 Al-Hlll C II 2H
CANARYls. CI-N10 All Bwl-Bw2 II Bw3ll Bw4 CI-Nll All C1II 2Bw-2BC CI-12 Al-A2-Bw-2Alb
GREECE GR-N13 Al-A2-C-Ck Gr-N14 A 1AC-C GR-N14a Ah 1 C
FRANCE FR-N15 Ah2-Ah3 1 Bw-C/R-R/C Bw-C/R-R/C 1R/C FR-N16 Ah 1 -Ah2-Ah3-Bwl -2Bw
HUNGARY HU-17 Ahl-Ah2-AC HU-N18 Ahl-Ah2A+R HU-N19 Ahl-Ah2-Bw+R
These results suggest that the elemental composition of the European volcanic soils
analyzed here is largely dependent on the parent material original mineralogy, a result already
suggested in previous studies (Buurman et al., 2003; Martínez Cortizas et al., 2003). But also
as found by Martínez Cortizas et al (2003) pedogenesis, organic matter content, climate
conditions and soil management by man are other important factors in the distribution of
some elements.
Very mobile elements (Ca, K, Sr) and even Zr, Th and U seem to have been leached in the
most evolved horizons and soils; while Cu, Zn, Pb and Hg show elevated concentrations in
the organic rich horizons, suggesting a role of the organic matter in their retention in the soils.
On the other hand, Br is more dependent on its extemal source (the ocean) and the dominant
climatic conditions, since the highest concentrations are found in the more oceanic (Azores)
and rainy areas (as it happens for the Italian soils). Finally, the degree of enrichment in Cu, Pb
and Hg in some soils (as for example Nl, and orchard soil) indicates that soil management
(i.e. fertilization and use of biocides) and atmospheric metal pollution are also significant
sources of some elements.
References
Buurman, P., García-Rodeja, E., Martínez Cortizas, A., and van Doesburg, J.DJ. 2003.
Stratification of parent material in European volcanic and related soils studied by laser-
diffraction grain-sizing and chemical analysis. Catena, 56: 127-144.
Martínez Cortizas, A., García-Rodeja, E., Nóvoa Munoz, J.C., Pontevedra Pombal, X.,
Buurman, P., and Terribile, F. 2003. Distribution of some selected major and trace elements
in four Italian soils developed from the deposits of the Gauro ad Vico volcanoes. Geoderma,
117: 215-224.
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